Nonlinear Constitutive Equations

Abstract

This chapter deals with how to measure nonlinear viscoelastic functions and various nonlinear viscoelastic constitutive equations. Since there have been developed a number of constitutive equations which cannot be included in a single chapter, this chapter considers only a few popularly used ones, which are classified to four groups: the models based on mathematical approximations; the models obtained from the generalization of linear viscoelastic models; the models based on the simplification of polymer structure; and the Leonov model which is a class of constitutive equations based on irreversible thermodynamics.